Gas turbine engines may be used to power various types of vehicles and systems, such as air or land-based vehicles. In typical gas turbine engines, compressed air generated by axial and/or radial compressors is mixed with fuel and burned, and the expanding hot combustion gases are directed against stationary turbine vanes in the engine. The gas flow deflects off of the vanes and impinges upon turbine blades of a turbine rotor. A rotatable turbine disk or wheel, from which the turbine blades extend, spins at high speeds. Gas turbine engines used in aircraft use power created by the rotating disk to draw more air into the engine and to pass high velocity combustion gas out of the gas turbine aft end to produce a forward thrust. Other gas turbine engines may use the power to turn a propeller or an electrical generator.
The engines may incorporate dual alloy turbine rotors. A dual alloy turbine rotor may include airfoils and outer rim rotor portions made of a first material having a desired characteristic and a hub made of a second material having another desired characteristic. For example, the airfoils and outer rim portions may include an alloy having relatively high creep rupture strength at the high temperatures, while the hub may be made of another alloy having high tensile strength and low-cycle-fatigue resistance properties.
To produce the dual alloy turbine rotors, a unitary blade ring made up of a ring of the airfoils is typically formed. The hub, which is fabricated separately from the blade ring, is then hot isostatically pressed, or otherwise bonded thereto. Manufacturing the dual alloy turbine rotor in the aforementioned manner has been relatively cost efficient and simple to perform.
The aforementioned dual alloy turbine rotors and manufacturing process may have several advantages, however, they may also have drawbacks. In some engines, for example, it would be desirable to operate dual alloy turbine rotors at gas temperatures that may be near or above an incipient melting point of one or both of the alloys. However, when subjected to these gas temperatures, the alloys may not exhibit the characteristics for which they were initially selected. Additionally, as the demand for more efficient and lightweight engines increases, inclusion of a dual alloy turbine rotor into an engine may not be feasible, as such rotors may be relatively heavier than conventional rotors.
Hence, there is a need for a dual alloy turbine rotor that may be used in extreme high temperatures. Moreover, it is desirable for the dual alloy turbine rotor to be relatively inexpensive, lightweight, and simple to manufacture.